A head up display (HUD) is a device that projects by means of optical reflection related information in front of a user, so as to allow the user to view images with his/her head up. Usually, an imaging position is in front of the user's eyes, and a height is basically flush with the user's eyes. Besides, the projected texts and images are adjusted onto an infinite focal distance, such that the user can easily integrate an ambient view with the related information when he/she looks at the front.
At present, after the HUD is fixed, an optical distance of each optical component therein is determined, and thus, the imaging position is also fixed. However, in consideration of scenes in which the HUD is applied, for example, when prompts are given with respect to the traffic conditions or the velocity during driving an automobile, if an object is present in front at the imaging position, it will inevitably prevent the user from viewing the information presented by the HUD, thus bringing inconvenience to the user and impairing the user experience.